docs: def guess_import_format(filename, **kwargs):
      '''
      guess_import_format(filename) attempts to guess the file format for the given filename; it does
        this guessing by looking at the file extension and using registered sniff-tests from
        importers. It will not attempt to load the file, so if the extension of the filename is
        missing, it is unlikely that this function will deduce the file-type (though load will often
        succeeed at extracting the data by trying all types exhaustively). If guess_import_format
        cannot deduce the format, it yields None.
  
      Note that if the filename has an extension that is recognized by neuropythy but the file itself
      is of another format, this function will never look beyond the extention in the filename;
      neither this function nor load perform that level of deduction.
      
      Keyword arguments that are passed to load should also be passed to guess_import_format.
      '''
      # first try file extension
      (_,filename) = os.path.split(filename)
      if '.' in filename:
          fnm = filename.lower()
          fmt = next((k for (k,(_,es,_)) in six.iteritems(importers)
                      if any(fnm.endswith('.' + e) for e in es)),
                     None)
          if fmt: return fmt
      # that didn't work; let's check the sniffers
      for (k,(_,_,sniff)) in six.iteritems(importers):
          try:
              if sniff(filename, **kwargs): return k
          except Exception: pass
      return None